Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$62.40	11.426%	$69.5298	$69.53	$69.55	$69.50
Purchase #2	$218.76	11.311%	$243.5039	$243.50	$243.50	$243.50
Purchase #3	$93.39	3.776%	$96.9164	$96.92	$96.90	$96.90
Purchase #4	$36.25	4.582%	$37.911	$37.91	$37.90	$37.90
Purchase #5	$35.72	4.839%	$37.4485	$37.45	$37.45	$37.40
Purchase #6	$248.73	9.742%	$272.9613	$272.96	$272.95	$273.00
Purchase #7	$56.83	13.694%	$64.6123	$64.61	$64.60	$64.60
7 purchase totals =	$752.08		$822.8832	$822.88	$822.85	$822.80